/*
 * Copyright � 2002-2011 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

namespace Spring.Pool;

/// <summary>
/// A simple pooling interface for managing and monitoring a pool
/// of objects.
/// </summary>
/// <remarks>
/// <p>
/// Based on the Jakarta Commons Pool API.
/// </p>
/// </remarks>
/// <author>Federico Spinazzi</author>
/// <seealso cref="Spring.Pool.IPoolableObjectFactory"/>
public interface IObjectPool
{
    /// <summary>
    /// Obtain an instance from the pool.
    /// </summary>
    /// <remarks>
    /// <p>
    /// By contract, clients <b>must</b> return the borrowed
    /// instance using <see cref="Spring.Pool.IObjectPool.ReturnObject"/>
    /// or a related method as defined in an implementation or
    /// sub-interface.
    /// </p>
    /// </remarks>
    /// <returns>An instance from the pool.</returns>
    /// <exception cref="Spring.Pool.PoolException">
    /// In case the pool is unusable.
    /// </exception>
    /// <seealso cref="Spring.Pool.IPoolableObjectFactory.ActivateObject"/>
    object BorrowObject();

    /// <summary>
    /// Return an instance to the pool.
    /// </summary>
    /// <remarks>
    /// <p>
    /// By contract, the object <b>must</b> have been obtained using
    /// <see cref="Spring.Pool.IObjectPool.BorrowObject"/>
    /// or a related method as defined in an implementation or sub-interface.
    /// </p>
    /// </remarks>
    /// <param name="target">The instance to be returned to the pool.</param>
    /// <seealso cref="Spring.Pool.IPoolableObjectFactory.PassivateObject"/>
    void ReturnObject(object target);

    /// <summary>
    /// Create an object using the factory set by
    /// the <see cref="PoolableObjectFactory"/> property
    /// or other implementation dependent mechanism
    /// and place it into the pool.
    /// </summary>
    /// <remarks>
    /// <p>
    /// This is an optional operation. AddObject is useful for "pre-loading" a
    /// pool with idle objects.
    /// </p>
    /// </remarks>
    /// <exception cref="NotSupportedException">
    /// If the implementation does not support the operation.
    /// </exception>
    void AddObject();

    /// <summary>
    /// Close the pool and free any resources associated with it.
    /// </summary>
    void Close();

    /// <summary>
    /// Clear objects sitting idle in the pool, releasing any
    /// associated resources.
    /// </summary>
    /// <remarks>
    /// <p>
    /// This is an optional operation.
    /// </p>
    /// </remarks>
    /// <exception cref="NotSupportedException">
    /// If the implementation does not support the operation.
    /// </exception>
    void Clear();

    /// <summary>
    /// Gets the number of instances currently borrowed from the pool.
    /// </summary>
    /// <remarks>
    /// <p>
    /// This is an optional operation.
    /// </p>
    /// </remarks>
    /// <exception cref="NotSupportedException">
    /// If the implementation does not support the operation.
    /// </exception>
    int NumActive { get; }

    /// <summary>
    /// Gets the number of instances currently idle in the pool.
    /// </summary>
    /// <remarks>
    /// <p>
    /// This is an optional operation.
    /// </p>
    /// <p>
    /// This may be considered an <i>approximation</i> of the number of objects
    /// that can be borrowed without creating any new instances.
    /// </p>
    /// </remarks>
    /// <exception cref="NotSupportedException">
    /// If the implementation does not support the operation.
    /// </exception>
    int NumIdle { get; }

    /// <summary>
    /// Set the factory used to create new instances.
    /// </summary>
    /// <remarks>
    /// <p>
    /// This is an optional operation.
    /// </p>
    /// </remarks>
    /// <exception cref="NotSupportedException">
    /// If the implementation does not support the operation.
    /// </exception>
    IPoolableObjectFactory PoolableObjectFactory { set; }
}
